Rotor for a rotary electrical machine comprising grooves for magnets

ABSTRACT

A rotor for an electrical machine that comprises two parallel magnet wheels, each of which comprises axial teeth so that each tooth on a wheel is situated in the space existing between two consecutive teeth on the other wheel, and that comprises magnetic elements, each arranged between two adjacent teeth and partly received in a groove produced in each of the opposite lateral faces of the two adjacent teeth In one embodiment, each of the two adjacent teeth comprises one groove at a maximum, which emerges at the base of the first tooth.

The invention concerns a rotor for a rotary electrical machine thatcomprises two parallel magnet wheels that extend radially with respectto a principal axis of the rotor, each of which comprises a series ofaxial teeth, roughly trapezoidal in shape, that extend axially from theexternal radial end edge of the said magnet wheel, in the direction ofthe other magnet wheel, so that each tooth on a magnet wheel is situatedin the space existing between two consecutive teeth on the other magnetwheel, and that comprise magnetic elements, such as permanent magnets,each of which is arranged between two adjacent teeth each belonging toone of the two magnet wheels, and is received partly in a grooveproduced in each of the opposite lateral faces of the said two adjacentteeth, so that at least one of the two lateral faces of a first tooth ofthe said two adjacent teeth comprises a groove in which a magneticelement is partly received, and so that each groove that is produced ina lateral face of a tooth of a rotor emerges at a first axial end of thetooth, where the first tooth is connected to the external radial endedge of the magnet wheel, or at a second free axial end of the tooth.The number of magnetic elements may be less than the number of teeth ona magnet wheel.

According to a known embodiment, the two grooves that are produced intwo opposite faces of two adjacent teeth are produced by means of asingle tool, for example a milling cutter, after the two magnet wheelsof the rotor have been mounted on a central shaft of the rotor.

It is also known how to produce all the grooves in the rotor so thatthey emerge at the same axial end of the rotor.

Consequently, when the two lateral faces of one and the same tooth on apole wheel each comprise a groove receiving a magnetic element, the twogrooves emerge axially either at a first axial end of the tooth wherethe tooth is connected to the edge of the radial end of the magnetwheel, or at the free axial end of the tooth, also referred to as thetip of the tooth.

The first axial end of the tooth, also referred to as the base of thetooth, where the tooth is connected to the magnet wheel, is then madeless resistant to deformation when the two grooves in the tooth emergeat this base of the tooth, compared with an embodiment according towhich the two grooves emerge at the free axial end of the tooth.

Thus, when the rotor is rotated at high speed, the reduction in theresistance to deformation of the base of the tooth means that the toothdeforms radially with respect to the rotor, and there is then a riskthat the tooth may come into contact with the stator of the rotatingelectrical machine.

The aim of the invention is to propose a rotor for a rotary electricalmachine for which the grooves receiving the magnetic elements areproduced so that the reduction in the elastic resistance to deformationof the base of each tooth is limited.

For this purpose, the invention proposes a rotor of the type describedabove, characterised in that each of the said two adjacent teethcomprises one groove at a maximum, which emerges at the base of the saidfirst tooth.

According to other characteristics of the invention:

each of the said two adjacent teeth comprises a groove produced solelyin one of its lateral faces, the two grooves being opposite each other,and the groove that is produced in the said lateral face of the firsttooth emerges at the base of the first tooth, and the groove that isproduced in the said lateral face of the second tooth of the said twoadjacent teeth emerges at the tip of the second tooth;

the two lateral faces of the first tooth each comprise a groove;

the two grooves that are produced in the two lateral faces of the firsttooth emerge at the tip of the first tooth;

a first one of the two grooves that are produced in the lateral faces ofthe first tooth emerges at the base of the first tooth and the secondone of the said two grooves that are produced in the lateral faces ofthe first tooth emerges at the tip of the first tooth;

each of the two lateral faces of each tooth comprises a groove thatpartly receives a magnetic element, and a single lateral face of eachtooth comprises a groove that emerges at the base of the associatedtooth, the other lateral face of the tooth comprising a groove thatemerges at the free axial end of the tooth, also referred to as the tipof the tooth;

the two grooves that are produced in the opposite faces of the twoadjacent tooth and that receive the same magnetic element both emerge atthe same axial end of the rotor; the magnet or magnetic element isintroduced between the two teeth on the side where the adjacent groovesemerge;

all the grooves emerge at the same axial end of the rotor;

all the grooves that are able to receive a magnetic element that issituated between a tooth on a first magnet wheel and a tooth on thesecond magnet wheel that is situated angularly upstream of the saidtooth on the first magnet wheel emerge at a first axial end of therotor, and all the grooves that are able to receive a magnetic elementthat is situated between a tooth on a first magnet wheel and a tooth onthe second magnet wheel that is situated angularly downstream of thesaid tooth on the first magnet wheel emerge at a second axial end of therotor;

the number of magnetic elements is equal to the total number of teeth onthe rotor;

the number of magnetic elements is less than the total number of teethon the rotor;

the rotor comprises at least one pair of magnetic elements, where eachmagnetic element in the pair is arranged, angularly with respect to theprincipal axis of the rotor, on each side of the first tooth;

the number of magnetic elements is equal to the number of teeth that asingle magnet wheel has, and each magnetic element is received between atooth on a first magnet wheel and a tooth on the second magnet wheelthat is situated angularly, with respect to the principal axis of therotor, upstream of the said tooth on the first magnet wheel. Themagnetic element is therefore always situated on the same side of eachtooth on the first magnet wheel.

The invention also proposes a method of producing a rotor, whichcomprises:

a step of assembling two magnet wheels so that each tooth on a magnetwheel is situated in the space existing between two consecutive teeth onthe other magnet wheel;

a step of machining the lateral faces of the teeth in order to producethe grooves receiving the magnetic elements, so that each of the twolateral faces of each tooth comprises a groove that is able to partlyreceive a magnetic element;

a step of mounting each magnetic element in two grooves that areproduced in the opposite faces of two adjacent teeth,

characterised in that the machining step comprises a first phase ofproducing the grooves that emerge at a first axial end of the rotor andthen a second phase of producing grooves that emerge at a second axialend of the rotor.

In this way the grooves that are able to receive a magnetic element thatis situated between a tooth on a first magnet wheel and a tooth on thesecond magnet wheel that is situated angularly upstream of the saidtooth on the first magnet wheel emerge at a first axial end of the rotorand the grooves that are able to receive a magnetic element that issituated on a tooth on a first magnet wheel and a tooth on the secondmagnet wheel that is situated angularly downstream of the said tooth onthe first magnet wheel emerge at a second axial end of the rotor. Inthis way machining is carried out once on one side of the rotor and onceon the other side. The grooves have an angle with respect to the base ofthe magnet wheels; this is because, each tooth being trapezoidal inshape, the inter-pole zone forms an angle towards the right on theleft-hand side of the tooth and an angle to the left on the right-handside of the tooth. The machining therefore takes place with a differentangle according to the side of the tooth. It is thus possible, forexample, to produce all the grooves oriented towards the left, that isto say the right-hand side of the tooth in question, and then all thegrooves oriented to the right, that is to say the left-hand side of thetooth in question.

According to other characteristics of the method according to theinvention:

each phase of the machining step consists of simultaneously producingthe two grooves in a pair of grooves, which are able to receive one andthe same magnetic element;

each phase of the machining step consists of producing successively thepairs of grooves that emerge at the same axial end of the rotor.

Other characteristics and advantages of the invention will emergeclearly from a reading of the following detailed description, for anunderstanding of which reference will be made to the accompanyingfigures, among which:

FIG. 1 is a schematic representation in perspective of the magnet wheelson a rotor of a rotary electrical machine, which comprises magnetsmounted in grooves produced in the teeth according to the invention;

FIG. 2 is a partial linear development with cutaway of the axial teethof the two magnet wheels depicted in FIG. 1, showing a first embodimentof the grooves according to the invention;

FIG. 3 is a view similar to that in FIG. 2, showing a second embodimentof the invention;

FIG. 4 is a view similar to those in FIGS. 2 and 3, showing a thirdembodiment of the invention;

FIG. 5 is a view similar to those in FIGS. 2, 3 and 4, showing a fourthembodiment of the invention.

In the description of the invention that follows, the orientation fromupstream to downstream will be used as being the tangential directionwith respect to the principal axis of the rotor and from left to rightas seen in FIG. 2. The bottom orientation corresponds to the bottom partof FIGS. 1 to 5.

FIG. 1 depicts a rotor 12 for a rotary electrical machine, such as forexample an alternator of the three-phase type, for a motor vehicle witha thermal engine, or an alternator/starter for in particular startingthe thermal engine of a vehicle.

The rotor 12 is a rotor of the claw type and comprises two magnet wheels20 juxtaposed axially and each having an annular-shaped radial flange 24that is provided at its external periphery with claws 26.

An excitation winding (not shown) is located axially between the flanges24 of the magnet wheels 20 and is carried by a part of the rotor 12 inthe form of a cylindrical core (not shown) coaxial with the magnetwheels 20.

Each claw 26 comprises a root portion 28 that is extended at itsexternal periphery by a tooth 30 with an axial principal orientationwith respect to the principal axis of the rotor 12.

The teeth 30 are trapezoidal in shape and are directed axially towardsthe flange 24 of the other magnet wheel 20, the tooth 30 of a magnetwheel 20 being received in the space existing between two consecutiveteeth 30 on the other magnet wheel 20, so that the teeth 30 on themagnet wheels 20 are interleaved.

Each tooth 30 comprises in particular an external axial end face 32 andtwo roughly planar lateral faces 68, forming two of the sides of thetrapezium.

Each lateral face 68 of a first tooth 30 belonging to a first magnetwheel 20 extends parallel to and at a substantially constant distancefrom an opposite lateral face 68 of a second tooth 30 belonging to theother magnet wheel 20.

Subsequently, two teeth 30, each of which belongs to one of the magnetwheels 20, and possessing a lateral face 68 opposite the lateral face 48of the other tooth 30, will be designated as being two adjacent teeth30.

The rotor 12 also comprises magnetic elements 62 such as permanentmagnets, which are interposed between two adjacent teeth 30, in order toreduce leakages of magnetic flux at the space between two adjacent teeth30, and in order to reinforce the magnetic flux.

According to one embodiment, the number of these magnets 62 isdetermined so that it is less than the number of teeth 30 on the rotor12.

In the embodiment of the rotor depicted in FIG. 1, each magnet wheel 20of the rotor 12 comprises eight teeth 30, and the rotor 12 thereforecomprises eight pairs of poles.

The number of magnets 62 on the rotor 12 can be determined so that it isless than the number of poles of the rotor 12, for example eight magnets62 for eight pairs of poles.

As can be seen in FIGS. 2 to 5, each magnet 62 that is interposedbetween two adjacent teeth 30 is received in a groove 70 produced ineach of the opposite lateral faces 68 of the two adjacent teeth 30.

Each groove 70, which is produced in a lateral face 68 of a tooth 30,extends in the roughly axial direction of the lateral face 68 of thetooth 30, between a base 30 a of the tooth 30 at which the tooth 30 isconnected to the root portion 28 of the claw 26 and therefore to theexternal radial end edge of the magnet wheel 20, and a second free axialend 30 b of the tooth 30, also referred to as the tip of the tooth.

According to a known embodiment, the two grooves 70 that are produced inthe two opposite lateral faces 68 of the two adjacent teeth 30 areproduced simultaneously, for example by milling, so that the two grooves70 both emerge at their axial end situated at one and the same axial endof the rotor 12, for example the bottom axial end, as depicted in FIG.3, so as to facilitate the introduction of the magnetic element.

Consequently, and as can be seen in FIGS. 2 to 5, one of the two grooves70 that are produced in the opposite lateral faces 68 and that receivethe same magnet 62 emerges at the base 30 a of the tooth 30, on thefirst magnet wheel 20, in which the groove is produced, and the othergroove 70 emerges at the tip 30 b of the tooth 30, of the second magnetwheel 20, in which this second groove 70 is produced.

In accordance with the invention, each tooth 30 that comprises a groove70 produced in one or other or both of its lateral faces 68, that is tosay each of the two adjacent teeth 30, comprises one groove 70 at amaximum that emerges at the base 30 a of the tooth 30.

Thus a single groove 70 in each tooth 30, or no groove 70 in each tooth30, emerges at the base 30 a of the tooth 30.

FIGS. 2 and 3 depict a first embodiment of the invention in which therotor 12 comprises a number of magnets 62 that is less than the numberof poles on the rotor 12, that is to say less than the number of teeth30 on the rotor 12. The magnets 62 can be mounted in pairs.

The two magnets 62 in the same pair are arranged on each side of a tooth30 on one of the two magnet wheels 20, which will be referred tohereinafter as the first tooth 30.

Each of the two lateral faces 68 of the first tooth 30 consequentlycomprises a groove 70 receiving one of the two magnets 62 of the pair ofmagnets, and the lateral face 68 of each of the two teeth 30 of theother magnet wheel 20 adjacent to the first tooth 30, which is oppositea lateral face 68 of the first tooth 30, also comprises a groove 70receiving one of the two magnets 62.

In accordance with the invention, at a maximum one groove 70 that isproduced in one of the lateral faces 68 of the first tooth 30 emerges atthe base 30 a of the first tooth 30.

According to a first embodiment of the invention depicted in FIG. 2, agroove 70 emerges at the base 30 a of the first tooth 30 here the groove70 that is situated downstream of the first tooth 30.

Consequently the other groove 70 that is produced in the first tooth 30and that is situated upstream of the first tooth 30 emerges at thesecond free axial end 30 b of the first tooth 30, and does not emerge atthe base 30 a of the first tooth 30.

In addition, the groove 70 that is produced in the lateral face 68 ofthe tooth 30 adjacent to the first tooth 30 and that is situatedupstream of the first tooth 30 emerges at the base 30 a of the saidtooth 30, and the groove 70 that is produced in the lateral face 68 ofthe tooth 30 adjacent to the first tooth 30 and that is situateddownstream of the first tooth 30 emerges at the tip 30 b of the saidtooth 30.

Consequently the two grooves 70 that receive the magnet 62 situatedupstream of the first tooth 30 emerge at a first axial end of the rotor12, here the bottom axial end, and the two grooves 70 receiving themagnet 62 situated downstream of the first tooth 30 emerge at the secondaxial end of the rotor 12, here the top axial end.

FIG. 3 depicts the second embodiment of the invention according to whichneither of the two grooves 70 produced in the lateral faces 68 of thefirst tooth 30 emerges at the base 30 a of the first tooth 30, that isto say they emerge at the tip 30 b of the tooth 30.

Consequently, the groove 70 that is produced in the lateral face 68 ofeach of the two teeth 30 adjacent to the first tooth 30 emerges at thebase 30 a of the said tooth 30.

According to this variant embodiment, all the grooves 70 that receivethe magnets 62 of the pair of magnets 62 associated with the first tooth30 emerge at the same axial end of the rotor 12, which is here thebottom axial end as seen in FIG. 3.

FIG. 4 depicts a third embodiment of the invention according to whichthe rotor 12 comprises a number of pairs of magnets 62 that is equal tothe number of poles on the rotor 12.

Consequently the rotor 12 comprises a magnet 62 that is arranged in eachspace existing between two adjacent teeth 30, and each tooth 30 on therotor 12 comprises a groove 70 produced in each of its two lateral faces68, which receives a magnet 62. There are therefore as many magneticelements as there are inter-pole spaces.

In accordance with the invention, a single groove 70 that is produced ineach tooth 30 emerges at the base 30 a of the tooth, that is to say itdoes not emerge at the tip 30 b of the tooth 30, and the other groove 70of the tooth 30 emerges at the tip 30 b of the tooth 30 and thereforedoes not emerge at the base 30 a of the tooth 30. It is then seen thatthe grooves 70 that receive the magnets 62 situated at a first side ofthe teeth 30 of a first magnet wheel 20 all emerge at the same axial endof the rotor 12, and, reciprocally, the groove 70 that received themagnets 62 situated on the other side of the teeth 30 on the firstmagnet wheel 20 all emerge at the other axial end of the rotor 12. Thegrooves thus in alternation and successively emerge at the top or at thebottom.

For example, here, the grooves 70 that receive the magnets 62 situateddownstream of the teeth 30 on the bottom magnet wheel 20 emerge at thebottom axial end of the rotor 12, and the grooves 70 that receive themagnets 62 situated upstream of the teeth 30 on the bottom magnet wheel20 emerge at the top axial end of the rotor 12.

FIG. 5 also depicts a fourth embodiment of the invention according towhich the rotor 12 comprises a number of magnets 62 that is equal to thenumber of teeth 30 that a single magnet wheel 20 has. In addition,according to this embodiment, only one lateral face 68 of each tooth 30comprises a groove 70.

Thus each tooth 30 on a magnet wheel 22 is associated with a singlemagnet 62, and two adjacent teeth 30 each belonging to one of the twomagnet wheels 20 and which are arranged on each side of a magnet 62 areassociated solely with this magnet 62.

In accordance with the invention, the groove 70 that is produced in alateral face 68 of a first tooth 30, for example here a tooth 30 on thebottom magnet wheel 20, emerges at the base 30 a of the first tooth 30,and the groove 70 that is produced in the opposite lateral face 68 ofthe other tooth 30 emerges at the tip 30 b of the second tooth 30.

Thus all the grooves emerge at the same axial end of the rotor 12, herethe bottom end of the rotor 12.

The invention also concerns a method for producing a rotor 12 accordingto which the grooves 70 that receive the magnets 62 emerge axially atthe top axial end or at the bottom axial end of the rotor 12, as is thecase for example with the embodiment of the rotor according to theinvention that was depicted in FIG. 4.

This method comprises a first step of assembling the two magnet wheels20 together, in particular by mounting both of them on a central shaft(not shown) of the rotor 12.

The method comprises a second step of producing grooves 70 in thelateral faces 68 of the teeth 30 by machining.

According to a preferred embodiment, the step of machining the lateralfaces 68 of the teeth 30 consists of a step of milling the teeth 30, soas to produce simultaneously the two grooves 70 in the same pair ofgrooves 70, which are able to receive the same magnet 62.

For this purpose, the milling cutter used for producing the grooves 70starts the teeth 30 by their end at which the grooves 70 emerge. That isto say by the ends 30 a, 30 b of the teeth 30 situated close to thebottom end of the rotor 12 when the two grooves emerge at the bottom endof the rotor 12, and/or by the ends 30 a, 30 b of the teeth 30 situatedclose to the top end of the rotor 12 when the two grooves emerge at thetop end of the rotor 12.

Finally, the method comprises a step of mounting the magnets 62 in thegrooves 70, by introducing them through the emerging ends of the grooves70.

According to the embodiment of the rotor 12 that is depicted in FIG. 4,the pairs of grooves 70, which each receive a magnet 62, emergealternately at the top axial end or at the bottom axial end of the rotor12.

In accordance with the invention, the machining step comprises a firstphase of producing the grooves 70 that emerge at a first end of therotor 12, for example the top end, and then a second phase of machiningthe other grooves 70 that emerge at the other end of the rotor 12, thebottom end for example. The machining is carried out on one side of therotor and then on the other side.

In addition, during each of the two phases of producing the grooves 70,the pairs of grooves 70 can be produced successively one after theother.

Thus, during the machining step, the milling cutter used for producingthe pairs of grooves 70 travels over a limited distance around the rotor12 between two machinings of pairs of grooves 70, and the duration ofeach machining step is then small compared with a conventional machiningstep according to which all the pairs of grooves 70 are producedsuccessively and independently of the end of the rotor 12 at which thegrooves 70 emerge.

The machining of the grooves on each side of the rotor can thus becarried out simultaneously with a tool comprising several millingcutters.

It will be understood that the invention is not limited to theembodiments that have just been described with reference to the figures,and that the rotor 12 can comprise a different number of magnets, and/orthat the magnets 62 can be arranged differently on the rotor 12 withoutdeparting from the field of the invention.

1. A rotor for a rotary electrical machine that comprises two parallel magnet wheels that extend radially with respect to a principal axis of the rotor, each of which comprises a series of axial teeth, roughly trapezoidal in shape, comprising a base and a tip, that extend axially from the external radial end edge of said magnet wheel, in the direction of the other magnet wheel, so that each tooth on a magnet wheel is situated in the space existing between two consecutive teeth on the other magnet wheel, and that comprise magnetic elements, each of which is arranged between two adjacent teeth each belonging to one of the two magnet wheels, and is received partly in a groove produced in each of the opposite lateral faces of said two adjacent teeth, wherein each of said two adjacent teeth comprises one groove at a maximum, which emerges at the base of a tooth.
 2. The rotor according to claim 1, wherein each of the said two adjacent teeth comprises a groove produced solely in one of its lateral faces situated opposite the groove in a lateral face of the other tooth of the said two adjacent teeth, and in that the groove that is produced in said lateral face of a first tooth emerges at an axial base of the first tooth, and the groove that is produced in said lateral face of a second tooth of said two adjacent teeth emerges at a free axial tip of the second tooth.
 3. The rotor according to claim 1, wherein the two lateral faces of a first tooth each comprise a groove.
 4. The rotor according to claim 3, wherein the two grooves that are produced in the two lateral faces of the first tooth emerge at the tip of the first tooth.
 5. The rotor according to claim 3, wherein a first one of the two grooves that are produced in the two lateral faces of the first tooth emerges at the base of the first tooth, and the second one of said two grooves that are produced in the two lateral faces of the first tooth emerges at the tip of the first tooth.
 6. The rotor according to claim 3, wherein each of the two lateral faces of each tooth comprises a groove that partly receives a magnetic element.
 7. The rotor according to claim 1, wherein the two grooves that are produced in the opposite faces of the two adjacent teeth and that receive the same magnetic element both emerge at the same axial end of the rotor.
 8. The rotor according to claim 7, wherein all the grooves that are able to receive a magnetic element that is situated between a tooth on a first magnet wheel and a tooth on a second magnet wheel that is situated angularly upstream of said tooth on the first magnet wheel emerge at a first axial end of the rotor, and in that all the grooves that are able to receive a magnetic element that is situated between a tooth on a first magnet wheel and a tooth on the second magnet wheel that is situated angularly downstream of said tooth on the first magnet wheel emerge at a second axial end of the rotor.
 9. The rotor according to claim 1, wherein the number of magnetic elements is equal to the total number of teeth on the rotor.
 10. The rotor according to claim 1, wherein the number of magnetic elements is less than the total number of teeth on the rotor.
 11. The rotor according to claim 10, wherein the rotor comprises at least one pair of magnetic elements, where each magnetic element in the pair is arranged, angularly with respect to the principal axis of the rotor, on each side of a first tooth.
 12. The rotor according to claim 11, wherein the number of magnetic elements is equal to the number of teeth that a single magnet wheel has, and in that each magnetic element is received between a tooth on a first magnet wheel and a tooth on the second magnet wheel that is situated angularly, with respect to the principal axis of the rotor, upstream of said tooth on the first magnet wheel.
 13. A method of producing a rotor comprising the steps of: assembling two magnet wheels so that each tooth on a magnet wheel is situated in the space existing between two consecutive teeth on the other magnet wheel; machining lateral faces of the teeth in order to produce the grooves receiving magnetic elements, so that each of the two lateral faces of each tooth comprises a groove that is able to partly receive a magnetic element; and mounting each magnetic element in two grooves that are produced in the opposite faces of two adjacent teeth; wherein the machining step comprises a first phase of producing the grooves that emerge at a first axial end of the rotor and then a second phase of producing grooves that emerge at a second axial end of the rotor, so that two adjacent teeth each comprise at a maximum only one groove emerging at the base of the tooth.
 14. The method according to claim 13, wherein each phase of the machining step consists of simultaneously producing the two grooves in a pair of grooves, which are able to receive one and the same magnetic element.
 15. The method according to claim 14, wherein each phase of the machining step consists of successively producing the pairs of grooves that emerge at the same axial end of the rotor.
 16. The rotor according to claim 5, wherein each of the two lateral faces of each tooth comprises a groove that partly receives a magnetic element.
 17. The rotor according to any claim 2, wherein the two grooves that are produced in the opposite faces of the two adjacent teeth and that receive the same magnetic element both emerge at the same axial end of the rotor.
 18. The rotor according to any claim 3, wherein the two grooves that are produced in the opposite faces of the two adjacent teeth and that receive the same magnetic element both emerge at the same axial end of the rotor.
 19. The rotor according to claim 3, wherein the number of magnetic elements is equal to the total number of teeth on the rotor.
 20. The rotor according to claim 5, wherein the number of magnetic elements is equal to the total number of teeth on the rotor.
 21. The rotor according to claim 3, wherein the number of magnetic elements is less than the total number of teeth on the rotor.
 22. The rotor according to claim 9, wherein the number of magnetic elements is less than the total number of teeth on the rotor. 